News agencies report the messages gave no details of the time, location or nature of the event that was to take place.

CNN reports that in two separate communications, persons in Afghanistan believed connected to Al-Qaeda appeared to be notifying others in Saudi Arabia that major attacks were imminent against the United States. However, the identities of the two persons originating the communications from Afghanistan are unknown.

The messages were not translated until September 12, one day after the attacks.

The NSA, based at Fort Meade, is the U.S.’s eavesdropping intelligence agency, intercepting millions of communications each hour - telephone conversations, e-mails, Internet traffic from satellites and listening posts around the world - prioritizing which intercepts need to be translated before others. It is one of the government's most secretive agencies.

The translated messages were "the subject of a lot of discussion" at a joint House-Senate intelligence committee meeting Tuesday, June 18, with NSA Director Michael Hayden, Federal Bureau of Investigation (FBI) Director Robert Mueller and Central Intelligence Agency (CIA) Director George Tenet testifying before the panel investigating September 11, said an official Wednesday.

CNN reports Hayden, responding to a question asking why it took the NSA two days to translate the intercepts, said the agency collects a lot of information daily, and it would be nearly impossible to translate all of it in a timely manner.

But U.S. authorities claim that even if the messages had been translated immediately, the contents of those conversations were too vague at that point, given the high number of similar messages intercepted daily by the NSA, and that a translation of those alone would not have been enough to warn and avert the attacks on September 11.

One U.S. official, on condition of anonymity, said the two messages were so non-specific that even had they been translated the same day they were intercepted, they would not have rung any alarm bells: "You know how many times we hear things much more serious than that? Lots of times," the official said, news agencies reported.

The joint congressional panel, in sessions already underway addressing the lack of intelligence and information sharing cooperation across various federal agencies, most notably the FBI and CIA, in questioning the department heads suggested that if there had been information-sharing between the various agencies, the likelihood of the intercepted messages, in conjunction with information each agency individually possessed at that time, could have made it easier to assess whether there was an imminent threat.

"I think people like Tenet, Mueller and Hayden feel very, very badly that they've let our government down and let the people down," one lawmaker said to CNN.

Scheduled public hearings, set to begin next week, have been delayed as a result of the revelation of the message intercepts.

One senior administration official, commenting on the vagueness of the intercepted conversations, said, "There had been a lot of chatter up there indicating something was up…But it does not say where, what and how reliable," reports the Washington Post.

Both the CIA and NSA have been criticized for failing to put sufficient emphasis on employing enough skilled translators and analysts to decipher the information it collects, reports the paper.

For its part, the NSA declined to comment on the intercepts. "I have no information to provide," said NSA spokeswoman Judy Emmel.